1. Technical Field
The present invention relates to a liquid ejecting apparatus, a drive circuit, and a driving method.
2. Related Art
An apparatus which uses a piezoelectric element (for example, a piezo element) is known as an ink jet printer which prints an image or a document by ejecting ink. Piezoelectric elements are provided in correspondence with each of multiple nozzles in a head unit and each of the piezoelectric elements is driven in accordance with a drive signal. A predetermined amount of ink (liquid) is ejected by such driving from the nozzle at a predetermined timing, and thereby, dots are formed. The piezoelectric element is a capacitive element such as a capacitor from a viewpoint of electricity, and needs to receive a sufficient current in order to operate the piezoelectric elements of each nozzle.
Accordingly, an ink jet printer has a configuration in which an original drive signal that is an origin of a drive signal is amplified by an amplification circuit, is supplied to a head unit as the drive signal, and drives a piezoelectric element. For example, D-class amplification is proposed as the amplification circuit (refer to JP-A-2010-114711). In short, in the D-class amplification, a pulse modulation of the original drive signal is performed, a high side transistor and a low side transistor serially inserted between the power supply voltages are switched in accordance with a modulation signal, an output signal generated by the switching is filtered by a low-pass filter, and thereby, the original drive signal is amplified.
However, a problem is pointed out in which a circuit configuration increases in size and waveform reproducibility of a drive signal with respect to an original drive signal is bad in the D-class amplification. In detail, in the D-class amplification, even in a case where, for example, an output voltage has to be kept constant, a high side transistor and a low side transistor are alternately switched, and thereby, a ripple caused by the switching easily ride. If it is intended to remove the ripple by using the low pass filter, a problem occurs in which a large capacitor and an inductor with a large L value are required as configuration elements of the low pass filter and thereby a device configuration is bulky and furthermore waveform reproducibility decreases due to a dull waveform.